[ntp:questions] Peers with and without PPS Source

Thomas Kayser forensic at milwpc.com
Mon Feb 12 21:41:40 UTC 2007

I have an interesting not really problem, but mystery.  I have 2 Debian Etch 
machines set up with Garmin 18 GPSs and PPS (Debian1-PPS and Debian2-PPS).  I 
have 2 other Debian Etch machines which have no PPS source directly attached 
to them (Debian3-NOPPS and Debian4-NOPPS).  The Debian1-PPS and Debian2-PPS 
use their own PPS source, and each other's PPS source, among other servers. 
Debian3-NOPPS and Debian4-NOPPS use both the Debian1-PPS and Debian2-PPS, 
among other servers.  On Debian1-PPS the offset for the Debian2-PPS time is 
in about 4 us, and vice versa.  On the NOPPS machines, the offsets for the 
PPS servers are 1-2 ms, and within us of each other.  

So, it seems if a machine has a PPS source, other PPS sources used by that 
machine will have much lower offsets than machines with no PPS source.  Is 
this a fluke?  We can try to solve this mystery, hopefully for better 
timekeeping for everyone.


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